The present invention relates to an improvement in a semiconductor integrated circuit and, more particularly, to a semiconductor integrated circuit which converts a power source voltage supplied to the integrated circuit and supplies the converted voltage to an internal circuit thereof.
An integrated circuit (to be referred to as IC hereinafter) for example, a CMOS static random-access memory, is known. In order to provide matching with external devices, a 5-V DC voltage is supplied to a IC as a power source voltage. The power source voltage is supplied to an internal circuit of the IC. The internal elements of the IC (e.g., MOS transistors forming individual memory cells) are micropatterned in accordance with the high integration of recent ICs. When a 5-V external power source voltage is applied to the micropatterned internal elements, the internal electric field is increased, and hot electrons with high energy are generated, thus degrading the element.
In order to solve this drawback, a memory device with the following arrangement has been proposed. An external power source voltage is supplied to a voltage converter circuit. The voltage converter circuit drops the input voltage and generates a low internal power source voltage. The internal power source voltage is supplied to an internal circuit (i.e., the internal elements constituting the circuit), and the circuit is operated on this voltage. With this arrangement, since a low voltage is supplied to the internal elements, hot electrons in the elements can be suppressed and degradation of the elements is prevented.
It is also known that a CMOS IC has a standby mode, in which the IC stops operation. For example, in the standby mode a SRAM stops operation while holding its storage contents. In this mode, the current consumption of the IC is decreased, e.g., to 0.5 .mu.A which is much lower than the current consumption (2 mA) in operation mode. Hence, ICs with low power consumption can be achieved. In the SRAM, storage contents can be held with a dry cell voltage. Thus, if a dry cell is used as a backup power source, the SRAM can be used as a nonvolatile memory device.
However, when the memory device capable of generating the internal voltage comprises a CMOS structure, the voltage converter circuit still requires power even if the internal elements consume almost no power in the standby mode. For this reason, the low power consumption of the CMOS structure cannot be taken advantage of in the standby mode. In fact, power consumption of the CMOS IC is actually increased.